Spring Croaker

A tree frog inflates its “vocal sac” and calls for a mate in a pond along Mill Creek. The vocal sac is a flexible membrane of skin possessed by most male frogs and is used to amplify their mating call. To call, air is expelled from the lungs, through the larynx, and into the vocal sac, which magnifies the sound.

 Mark Gibson

A tree frog inflates its “vocal sac” and calls for a mate in a pond along Mill Creek. The vocal sac is a flexible membrane of skin possessed by most male frogs and is used to amplify their mating call. To call, air is expelled from the lungs, through the larynx, and into the vocal sac, which magnifies the sound.